1. Field of the Invention
The present invention relates to a packing container for an electronic instrument to protect it from a shock, and especially relates to a packing container suitable for comparatively thin and lightweight electronic instrument.
2. Description of the Related Art
In a packing container for electronic instrument made of a corrugated fiberboard, cushioning members are used at corners of the packing container for supporting the electronic instrument so as not to be damaged due to a shock, or the like, while the transportation. The cushioning member is generally made of foaming resin such as polystyrene, and has a problem on environment when it is disposed after use.
Therefore, various packing containers are conventionally proposed for solving the above-mentioned problem. For example, Publication of Unexamined Japanese Patent Application No. 9-104432 or 6-135461 shows a packing container in which inside flaps are bent for forming cushioning portions to protect the electronic instrument from a shock. The cushioning members, however, are formed by bending the inside flaps simply, so that the cushioning portions are going to be restored while the electronic instrument is accommodated in the packing container. Thus, it is necessary to steady the cushioning portions by hands so as not to restore. It causes the deterioration of the workability.
In another packing container, for example, shown in Publication of Unexamined Japanese Utility Model Application No. 49-31732, arrow shaped projections are formed on front ends of the cushioning portions so as to be fitted into slits formed on bottom flaps for preventing the restoration of the cushioning portions. There, however, is a problem that the projections are easy to come off from the slits because dimensions of the arrow shaped projections projected from the bottom face of the bottom flaps are small. Even if the dimensions of the arrow shaped projections projected from the bottom face of the bottom flaps are made larger to solve such a problem, the arrow shaped projections projected from the bottom face of the bottom flaps cause the interference when multiple packing containers are piled up. Thus, it becomes difficult to pile up the packing containers in a manner to align the side faces of the piled packing containers, and the piling up of the packing containers becomes unstable.
In still another packing container, for example, shown in Publication of Unexamined. Japanese Patent Application No. 10-29626, fixation projections are formed in circumferences of outer bottom flaps to prevent the restoration of the cushioning portions. Even when the packing container is thin that the height dimension (corresponding to a dimension L shown in FIG. 3) of the inner bottom flap is substantially the same as that of the outer bottom flap, the fixation projections will protrude from the circumferences of the inner bottom flaps and the outer bottom flaps in a developed state before assemble the packing container. Therefore, when several packing containers are mass-produced from one piece of corrugated fiberboard, unavailable odd pieces increase, and it is difficult to reduce the cost of the packing container.
In still another packing container, for example, shown in Registered Japanese Utility Model No. 25661309, an inner side bottom flap is adhered on a pressing piece formed on a bottom flap for increasing reaction force of the pressing piece so as to hold an ingredient firmly. Since the assemble of the packing container needs processes for spreading adhesive on the inner side bottom flap and for crimping the inner side bottom flap and the pressing piece, it is burdensome to assemble the packing container and it is difficult to reduce the cost of the packing container.
Still furthermore, in the above-mentioned conventional packing containers, top cushioning portions and bottom cushioning portions are departed from each other, so that a load applied to the packing container in vertical direction must be supported only by side boards of the packing container. Therefore, if the packing container is dropped due to mistake, the side boards were easy to do buckling, and there was a fear that large stress was applied to the accommodated electronic instrument.